Anyone ever dealt with exhaustion

Not heat exhaustion or anything like that. But the type where your doctor pulls you out of work for a couple weeks and tells you he is not sure when you can go back. Is this really that serious? I'm asking for a cousin who's ex is saying he may not be able to go back to work. And now she is concerned he may not be able to continue any support for their kids. Thanks

Maybe the Dr will find out he has something he just has to take medicine for (maybe long term??? I take 2 kinds) then he can go back to work. Lots of people are on a med. and go to work everyday.
It could be 'nothing much'.

He needs a reason for the exhaustion, as in a diagnosis. No one should just be labeled "exhausted" with no cause. It could be anything from depression to an infection, to cancer. Make him get a real diagnosis, not just a pass off work.